Membranes are known which include a reinforcement having an asphaltic based coating thereon and including a pressure sensitive adhesive on one side thereof. U.S. Pat. Nos. 3,741,856 and 3,900,102 exemplified such membranes.
The above incorporated copending applications also disclose such membranes in the form of a laminate comprising a membrane of a coated fibrous reinforcement material having an adhesive layer on one side thereof. The asphaltic based coating is a substantially non-tacky reaction product of asphalt, a polymerizable vinyl aromatic monomer, a non-depolymerized rubber, a terpene resin and depolymerized rubber, i.e., rubber which has been treated with a depolymerizing agent to decrease its molecular weight. While such laminates have many outstanding properties making them well adapted for use in the highway repair and maintenance industries, including both highway and road repair, driveway repair, parking lot repair and maintenance, airport runway repair and maintenance, and the repair and maintenance of like vehicular supporting structures, these laminates, and, more specifically, the adhesive, need to be improved with respect to their low temperature flexural strength properties and thermal sensitivity. Adhesives, which have been employed in the above laminates and which have been manufactured from AC-20 paving grade asphalt, exhibit flexural strength characteristics down to on the order of about 15.degree.-17.degree. F. AC-20 paving grade asphalt has a penetration of about 40 to about 60 or 65 and has a viscosity at 200.degree. F. of about 4000 cps, or higher, and a viscosity at 325.degree. F. of in excess of 100 cps and most typically about 110-112 cps. As is disclosed in the incorporated applications, the adhesives are heated and applied to one side of the asphaltic coated reinforcement as a hot melt. It has been noted that such heated adhesives, when held in a molten condition for prolonged time periods, develop the formation of relatively hard, small granules, i.e., they are thermally sensitive. This thermal sensitivity which results in hard granule formation impairs the efficiency and economy of manufacturing such laminates.
Consequently, there is a need to provide for improved laminates and, more specifically, for improved adhesives which have superior low temperature flexural strengths, that is, satisfactory flexural strengths at lower temperatures and which are thermally insensitive and will not form undesirable hard granules when being held in a melt stage for prolonged time intervals. In accordance with the present invention, such improved adhesives, as well as improved laminates, are provided for use in the repair and maintenance of vehicular supporting structures. The invention resides in a composition which is thermally insensitive, has good adhesion to cementitious substrates, such as, for example, asphalt and concrete substrates, and has good low temperature flexural strengths, that is, good flexural strengths down to temperatures on the order of less than about 0.degree. F. and generally about 0.degree. F. to about -2.degree. F. The adhesive consists essentially of the reaction product of an asphalt flux, a polymerizable vinyl aromatic monomer, a non-depolymerized rubber which is a homopolymer of a conjugated diene or a copolymer of a conjugated diene and at least one ethylenic monomer copolymerizable therewith, a terpene resin and a depolymerized rubber, i.e., a rubber which has been treated with a depolymerizing agent to decrease its molecular weight.